Constituents of an Organic Wood Preservative That Inhibit the Fluoranthene-Degrading Activity of <i>Sphingomonas paucimobilis</i> Strain EPA505

Abstract

Sphingomonas paucimobilis strain EPA505 is capable of utilizing many components of coal tar creosote as sole sources of carbon and energy for bacterial growth, including fluoranthene and other polycyclic aromatic hydrocarbons (PAH). During several bioremediation studies, however, we observed that the fluoranthene degradative activity of strain EPA505 was inhibited by the presence of undefined creosote constituents. In practice, integration of a pretreatment step prior to inoculation with strain EPA505 was necessary to facilitate the biodegradation of high molecular weight (HMW) PAHs. Experiments were thus initiated to determine which compound classes in creosote inhibited fluoranthene metabolism by strain EPA505. Creosote was fractionated by solvent extraction at various pH, and three chemical classes were examined: acid (phenolics), base (N-heterocyclics), and neutral (PAH). The mineralization rate of 14C-labeled fluoranthene and cell viability were examined in the presence of these creosote fractions at a range of concentrations. These studies confirm that strain EPA505 has differing susceptibility to the effects of the three classes of creosote constituents. The observed order of toxicity/inhibition was basic fraction > acidic fraction > neutral fraction. These studies provide engineering guidelines and define contamination ranges under which strain EPA505 can be used most effectively as a catalyst in bioremediation (Figure 4).